One vertex per element, one color per generator, with an edge from x to x·s.
(1,2,4,6,5,7,3,8)(9,10,14,19,15,20,13,18)(11,21,25,32,24,31,23,16)(12,26,28,33,29,17,27,34)(22,35,38,30,37,40,36,39)(2,6)(3,4)(7,8)(9,11)(10,16,20,32)(12,22)(13,23)(14,25)(15,24)(17,30,26,39)(18,31,19,21)(27,36)(28,38)(29,37)(33,35,34,40)(9,12,15,29)(10,17,20,26)(11,22,24,37)(13,28,14,27)(16,30,32,39)(18,34,19,33)(21,35,31,40)(23,38,25,36)(2,7)(6,8)(9,13,15,14)(10,18,20,19)(11,23,24,25)(12,27,29,28)(16,31,32,21)(17,33,26,34)(22,36,37,38)(30,35,39,40)A Cayley diagram is a choice, not a fact about the group. Another drawing of this group — in a book, or on a different generating set — may look nothing like this one.